Answer

This information applies to I/O subsystem configurations using R720 or R730 support for 4096 byte sectors and the SMFSCLEAN tasks. The disk drives will show up as D/TD840 or D/T6B4E-050. This includes 4K sector SSDs attached through VIOS natively and attached Flash systems FS840 and FS900. This does not include native attached 4K SSDs with 4160 sector size or flash attached through VIOS or SVC.

This document describes the most common setting used for the SetDirtyFreeSpace macro. These settings are used to tune the aggressiveness of the SMFSCLEAN* tasks. All of the settings take affect immediately and will remain set across IPLs.

Adjusting the macro settings to be more aggressive does take affect immediately, but an IPL after running the macro may provide faster relief from the performance issue described here: http://www-01.ibm.com/support/docview.wss?uid=nas8N1021895

*Setting 2 is the most common adjustment.
Consider if these settings should be made on other partitions.

There are multiple sections below:
a) Determine the current settings
b) Reset to default settings
c) Setting 1
d) Setting 2*
e) Setting 3
f) Explanation of settings

a) Determine the current settings:

o STRSST <enter>
o Specify credentials <enter>
o 1. Start a service tool <enter>
o 4. Display/Alter/Dump <enter>
o 1. Display/Alter storage <enter>
o 2. Licensed Internal Code (LIC) data <enter>
o 14. Advanced analysis <enter>
o Specify Option 1 and SETDIRTYFREESPACEKNOBS <enter>
Option Command
1 SETDIRTYFREESPACEKNOBS
o Specify -Q on Options <enter>
Options . . . . . -Q
o Press <enter> on the options screen
o Note the settings
o Exit SST

Example output:
DISPLAY/ALTER/DUMP
Running macro: SETDIRTYFREESPACEKNOBS -Q
...
...


b) Reset to default settings:

o STRSST <enter>
o Specify credentials <enter>
o 1. Start a service tool <enter>
o 4. Display/Alter/Dump <enter>
o 1. Display/Alter storage <enter>
o 2. Licensed Internal Code (LIC) data <enter>
o 14. Advanced analysis <enter>
o Specify Option 1 and SETDIRTYFREESPACEKNOBS <enter>
Option Command
1 SETDIRTYFREESPACEKNOBS
o Specify -R on Options <enter>
Options . . . . . -R
o Press <enter> on the options screen
o Exit SST

Example output:
DISPLAY/ALTER/DUMP
Running macro: SETDIRTYFREESPACEKNOBS -R

reset all values back to defaults.

** Note that the default setting changes with TR6:
Throttle value: 0000000000000019

** Below are the defaults prior to TR6:
old throttle value: 0000000000000002
new throttle value: 0000000000000002

old baseTime: 0000000000000001
new baseTime: 0000000000000001

old number of System Cleanup Tasks: 0000000000000000
new number of System Cleanup Tasks will be calculated from number of disk unit

old number of Cleanup Tasks in each IASP: 0000000000000000
new number of Cleanup Tasks in each IASP will be calculated from number of disk



c) Setting 1:

o STRSST <enter>
o Specify credentials <enter>
o 1. Start a service tool <enter>
o 4. Display/Alter/Dump <enter>
o 1. Display/Alter storage <enter>
o 2. Licensed Internal Code (LIC) data <enter>
o 14. Advanced analysis <enter>
o Specify Option 1 and SETDIRTYFREESPACEKNOBS <enter>
Option Command
1 SETDIRTYFREESPACEKNOBS
o Specify -T 1 on Options <enter>
Options . . . . . -T 1
o Press <enter> on the options screen
o Exit SST

Example output:
DISPLAY/ALTER/DUMP
Running macro: SETDIRTYFREESPACEKNOBS -T 1

old throttle value: 0000000000000002
new throttle value: 0000000000000001



d) Setting 2:

o STRSST <enter>
o Specify credentials <enter>
o 1. Start a service tool <enter>
o 4. Display/Alter/Dump <enter>
o 1. Display/Alter storage <enter>
o 2. Licensed Internal Code (LIC) data <enter>
o 14. Advanced analysis <enter>
o ***Specify Option 1 and SETDIRTYFREESPACEKNOBS <enter>
Option Command
1 SETDIRTYFREESPACEKNOBS
o Specify -T 0 -SR 10 on Options <enter>
Options . . . . . -T 0 -SR 10
o Press <enter> on the options screen
o Exit SST

Example output:
DISPLAY/ALTER/DUMP
Running macro: SETDIRTYFREESPACEKNOBS -T 0 -SR 10

old throttle value: 0000000000000019
new throttle value: 0000000000000000

old number of System Cleanup Requests Value: 10
new number of System Cleanup Requests Value: 10



e) Setting 3:

o STRSST <enter>
o Specify credentials <enter>
o 1. Start a service tool <enter>
o 4. Display/Alter/Dump <enter>
o 1. Display/Alter storage <enter>
o 2. Licensed Internal Code (LIC) data <enter>
o 14. Advanced analysis <enter>
o Specify Option 1 and SETDIRTYFREESPACEKNOBS <enter>
Option Command
1 SETDIRTYFREESPACEKNOBS
o Specify -T 0 -SR 20 on Options <enter>
Options . . . . . -T 0 -SR 20
o Press <enter> on the options screen
o Exit SST

Example output:
DISPLAY/ALTER/DUMP
Running macro: SETDIRTYFREESPACEKNOBS -T 0 -SR 20

old throttle value: 0000000000000019
new throttle value: 0000000000000000

old number of System Cleanup Requests Value: 20
new number of System Cleanup Requests Value: 20



f) Explanation of settings:

Defaults:
SETDIRTYFREESPACEKNOBS -R
Throttle value: 0000000000000002
throttleValue == 2: if DFS <= 50% pause, else keep cleaning
BaseTime: 0000000000000001
Number of System Cleanup Tasks will be calculated from number of 4k disk units
Number of Cleanup Tasks in each IASP will be calculated from number of 4k disk

Setting 1:
SETDIRTYFREESPACEKNOBS -T 1
throttleValue == 1: if DFS <= 25% pause, else keep cleaning

Setting 2:
SETDIRTYFREESPACEKNOBS -T 0 -SR 10
throttleValue == 0: don't pause at all, just keep cleaning
numberOfSystemCleanupRequest == 10 indicates the system will create 1x as
many cleanup tasks as there are 4k disk units in traditional ASPs.
*** Prior to PTFs MF63512 (R720) and MF63604 (R730) the equivalent option was:
-T 0 -S -1

Setting 3:
SETDIRTYFREESPACEKNOBS -T 0 -SR 20
throttleValue == 0: don't pause at all, just keep cleaning
numberOfSystemCleanupRequest == 20 indicates the system will create 2x as
many cleanup tasks as there are 4k disk units in traditional ASPs.
**** Prior to PTFs MF63512 (R720) and MF63604 (R730) the equivalent option was:
-T 0 -S (# of luns * 2)